The high field tokamak path to fusion energy: C-Mod to SPARC to ARC

Applying results from the world-wide tokamak experimental databases, we map out a path to realizing fusion energy using the high magnetic field tokamak approach. With conservative assumptions about H-mode confinement, a pre-conceptual design for a net energy gain D-T facility, SPARC, yields Q>2, and possibly much higher, in a medium scale, conventional aspect ratio tokamak with R≈1.6m, B_T=12T. The I-mode regime should also be accessible, and could yield similar or higher performance. SPARC will use high-field, high temperature REBCO superconductors to access burning plasma regimes. Extrapolation to a somewhat larger, slightly lower-field design, ARC[1], can produce on the order of 500 MW of fusion power, and would put electricity on the grid. The extrapolation to SPARC relies heavily on the high-field results from Alcator C-Mod. We present details of the SPARC design, and consider physics challenges in operational regimes and limits, heating, fast particle instability drive, and divertor power and particle handling.

[1] B.N. Sorbom, et al., Fus. Eng. Des. 100(2015)378.